The present invention relates to an individual cell (and to a construction method therefor) for a battery having an electrode stack disposed inside a cell housing, with the individual electrodes (preferably electrode foils) being electrically connected to lead vanes, and at least electrodes of different polarities being separated and insulated from each other by a separator (preferably a separator foil). Lead vanes of the same polarity are connected to each other in an electrically conductive manner to form a pole. Such a battery (and method) may, for example, be used in energy technology, especially in battery-operated vehicle technology.
Especially with lithium ion cells for mild hybrid vehicles, which are designed as flat cells in a sensible manner, aluminum and copper foils coated with electrochemically effective materials are used as electrode foils. The electrode foils are stacked on top of each other to form an electrode stack, wherein the individual electrode foils are separated from each other electrically and also spatially by a separator, preferably also formed as a foil. The contacting of an electrode foil to the outside takes place by means of a lead vane welded to the electrode foil, which has to be guided through the cell housing. As the cell housing of an individual cell is usually formed of metal, preferably aluminum, the lead vanes have to be insulated electrically amongst others in the feedthrough region. The tightness of the cell housing in the feedthrough region can only be manufactured with difficulty and very elaborately. This problem relates to the compression strength and also the sealing against humidity. Thus, the entry of humidity is still a very difficult problem, which can only be solved in a very elaborate manner.
One object of the present invention, therefore is to provide an improved individual cell for a battery and an improved method for its production, which especially overcome the disadvantages given in the state of the art and that the production costs are reduced as much as possible.
This and other objects and advantages are achieved by the cell structure and method according to the invention, in which electrical poles can be guided from the interior of the individual cell to the outside by contacting between the lead vanes of the electrode foils of individual cells of a battery, without elaborate sealing measures. The contacting thereby especially takes place by means of welding an associated outer side, so as to contact the interior electrode foils with the outside.
In a special manner, a peripheral (edge) region of the respective electrode foil guided to the outside of the electrode stack is used as the lead vane, whereby complex contacting of electrode foil and lead vane is unnecessary. This type of contacting is at the same time very safe against at least many, especially outer influences such as impacts or vibrations.
In a special manner, especially with bipolar individual cells, the contacting takes place directly to the opposite outer, especially flat sides of the cell housing, wherein these outer, especially flat sides are electrically insulated with regard to each other. In this manner, lead vanes of one polarity are welded and/or compressed directly to an outer side, preferably a flat side of the cell housing, especially a flat cell, wherein the outer sides of different polarity are electrically insulated from each other.
By an arrangement of the electrode stack with a frame running circumferentially around the edge, which is especially electrically insulating, an additional insulating arrangement can be saved in an advantageous manner. The manageability of the individual cell is further eased or designed in a safer manner.
In a further development of the invention, a frame running circumferentially around the edge, and which is electrically insulating, is arranged between two electrically conducting flat sides of the cell housing, which frame has two material recesses electrically insulated from each other and spaced from each other. The lead vanes of one polarity are arranged in these material recesses. In an advantageous manner, the clear height measured in the direction of the stacking of the electrodes of a material recess is smaller or the same as the corresponding extension of the associated lead vanes stacked above each other in an uninfluenced manner, and their depth measured parallel to the flat side of an electrode foil is larger or the same as the corresponding extension of the associated lead vanes. The lead vanes are hereby held securely in the material recesses and can be compressed with these in an electrically conductive manner with an especially tight connection between the frame and the outer/flat sides.
According to a further advantageous embodiment of the invention, the electrical connection between the cell housing and a “+” or “−” pole at the electrode stack is only produced during and especially after the assembly of the cell housing, and namely from the outside by a welding and/or compressing method, in a preferred manner by means of a laser beam welding method.
In a preferred manner, the housing wall of the respective outer side and further in the depth, the lead vanes of the electrode stack are partially melted on during a welding method, whereby a material-fit connection can be produced.
According to further an advantageous development of the invention, a weld seam comprises, seen in the direction of the stacking of the electrodes, all lead vanes or passes through these.
According to a further development of the invention, a weld seam comprises, seen in the direction of the stacking of the electrodes, not only all lead vanes, but also the corresponding electrically conductive outer side of the cell housing of the individual cell or passes through it.
In an advantageous further development, the connection of the corresponding flat side of the cell housing, especially of an aluminum housing with a copper foil as a pole, can be improved by inserting a foil of additional material, e.g. nickel.
According to an advantageous further development of the invention, poles are only switched to the corresponding outer sides with a final welding process taking place on corresponding outer sides, especially flat sides of the cell housing.
By one or more of the mentioned measures, it is possible to simplify the construction of a cell housing with an inexpensive production, to increase the safety against vibration and thus the stability, the durability, and thereby again also the usage diversity, to enable a good installation space usage within a battery box, especially also through the contacting positions which are now possible. The failure rate is also reduced by the simplified contacting method. Furthermore, by the simple contacting at the closed individual cell, their production is eased considerably. Furthermore, the current capacity is improved by the material-fit contacting of the lead vanes. A weakening of the pressure tightness of the cell housing of the individual cell is also not present, as no contact feedthrough of the poles takes place. The improvement of the tightness of the interior of the cell housing with regard to the entrance of humidity is also connected directly hereby.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.